Author: José de Jesús García Ruvalcaba
Date: 15:15:35 01/22/00
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On January 22, 2000 at 00:46:51, Len Eisner wrote: >On January 22, 2000 at 00:22:07, Robert Hyatt wrote: > >>On January 21, 2000 at 08:34:23, Steve Coladonato wrote: >> >><snip> >> >>> >>>Dave, >>> >>>One last question then. Given that the tablebase position is a mate in 15, how >>>do you know that the one ply search is choosing the correct move? >>> >>>Steve >> >> >>Easy. All the TBs have are mate-in-n, mated-in-n, or draw scores, for every >>possible position for all the pieces. ALl you have to do is generate the >>ply-1 move list, make each one, and probe the TB for the exact score after >>that move. Take the move that leads to the best score. Which will be the >>shortest mate if winning, the longest mate if losing, or any move that draws >>if all the moves lead to draw or loss. >> >>Think of it as a "perfect" evaluation function for positions with 5 or fewer >>total pieces on the board.. > >How do you handle situations where all moves draw, but some moves are much >better than others. > >For example, in the following position, how do you differentiate between f5, >which continues the fight, and Rg3 which hangs the pawn. Both moves draw, but >f5 is clearly better against a human who may not know how to play the position >perfectly. > >[D] 4k3/5r2/8/8/5P2/3K1R2/8/8 w - - 0 1 > >Len Some programs play any move that keeps the draw (not very smart). Crafty enters its "swindling mode", it does a normal search but only for the non-losing moves for both sides (this is an example of what I call good tablebase handling). José.
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